This invention relates to gang sawing and chipping systems, and more particularly to such systems in which the gang saw is movable in two dimensions to saw a curved cant according to its curvature.
U.S. Pat. No. 5,722,474 to Raybon et al (incorporated herein by reference) discloses a method and apparatus for cutting a curved cant into boards. A scanner detects curvature of the cant and this information is used to control the position of a gang saw mounted on a pivot axis to cut the cant into substantially even thickness boards while moving the cant past the saws and pivoting the gang saw to accommodate the curvature of the cant.
Raybon et al have in-feed and out-feed conveyors positioned on opposite sides to a pivotable gang saw structure, and FIG. 7 shows chipping heads mounted in the out-feed conveyor assembly to remove the wane slabs from lateral sides of the sawn cant. The chipping heads are movable laterally to accommodate different dimensions of cants, and are driven from a pair of motors mounted atop the out-feed conveyor assembly via U-jointed drive shafts. The out-feed conveyor assembly is static, in contrast to the laterally pivotable gang saw assembly, so the chipping head drive need only accommodate movement of the chipping heads in one direction.
Using an out-feed chipping arrangement is disadvantageous for a number of reasons that make it preferable to perform the chipping operation before the cant is sawn rather afterward. It is known to use in-feed-side chipping heads in connection with a gang saw that is static or only laterally movable, with the chipping heads mounted in the infeed conveyor. This arrangement will not work, however, with a gang saw assembly that is movable in two dimensions as in the Raybon et al system. It is also impractical to try to mount the drive motors on the movable gang saw assembly because the gang saw assembly must be moved quite quickly from on position to another during sawing and the motors are too heavy to permit such quick movement.
One of the inventors named in Raybon et al, R. McGehee, has attempted to overcome this problem, by mounting the chipping heads in the entrance to the gang saw assembly to be movable in one lateral direction along rods and movable in a second direction along with the gang saw assembly. In order to provide drive power to the chipping head, the drive motors are mounted to one side of the outfeed frame assembly and coupled to the chipping heads through an articulating pantograph arm structure supporting a series belts and pulleys. This is a cumbersome, expensive and breakdown prone arrangement.
Accordingly, a better way is needed to provide in-feed-side chipping in a cant-sawing system having a gang saw that is pivotable or otherwise movable in two lateral dimensions.